The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Metal contamination of substrates such as semiconductor wafers leads to degradation of device performance and yield loss. The International Technology Roadmap for Semiconductors (ITRS) maintains a forecast of technology requirements for semiconductor processing including guidelines on acceptable metal contamination levels of semiconductor wafers. As feature sizes continue to decrease, the acceptable level of metal contamination also decreases.
Forming gas (FG) is commonly used as a process gas during plasma processing such as photoresist stripping. Forming gas includes 4% molecular hydrogen and 96% molecular nitrogen. Forming gas tends to generate excessive concentrations of copper during plasma processes in substrate processing chambers that include components made from alloys including copper. For example only, 6061 aluminum alloy includes 95.85% to 98.56% aluminum, 0.15% to 0.40% copper and other metals. 6061 aluminum alloy is widely used to manufacture components in the processing chamber that are exposed to plasma. When 6061 aluminum alloy is located in a plasma processing chamber where forming gas is used as the process gas, copper in the aluminum alloy may react with process gas and become volatile and may transport to and contaminate the substrates.
One approach for reducing copper contamination involves plasma conditioning of the substrate processing chamber. The plasma conditioning generally requires one or more weeks to perform and generates inconsistent results. Another approach is to manufacture the processing chamber components using metals that do not include copper. This approach may increase the cost of the substrate processing tool and may increase the risk of a performance shift that may generate other issues.